Copy constructors

Copy constructors

Copy constructors are always used when the compiler has to create a temporary object of a class object. The copy constructors are used when the initialization of an object is to be done by another object of the same class.

The general format of the copy constructor is,

            class_name(class_name &object)

e.g.

     class copyConst

              {

                  …..

                 public:

                 copyConst(copyConst &ob);         

      };

Example:

class sample

{

      int id;

   public:

    sample (int x)          //constructor again defined with passing arguments

      {     id=x;      }

     sample(sample & obj)        //copy constructor

      {  id=obj.id; } //copy in the value

      void display()

      {  cout<<id;  }

};

void main()

{  sample ob1(100);     // object a is created and initialized

   sample ob2(ob1);     // copy constructor called

   sample ob3(ob2);     // copy constructor called again

   cout<<"\nId of ob1: ";

   ob1.display();

   cout<<"\nId of ob2: ";

   ob2.display();

   cout<<"\nId of ob3: ";

   ob3.display();

 }

Output:

Id of ob1: 100

Id of ob2: 100

Id of ob3: 100